We have concentrated on the analysis of the expression of the erythroid proteins band 3 and ankyrin in adult cardiac muscle cells and during cardiac myogenesis. In erythroid cells these two proteins interact as part of the membrane skeleton of these cells. With respect to ankyrin, erythroid ankyrin cDNA probes detect an ankyrin transcript in cardiac muscle cells that is less than half the size of the erythroid transcript (8.8 vs. 3.5 kb). To elucidate the structural divergence of ankyrin in erythroid and cardiac muscle cells, we have isolated overlapping cDNA clones for ankyrin from an erythroid cDNA library. Thus far the clones cover approximately 5 kb of the erythroid ankyrin transcript. We are in the process of isolating more overlapping clones as well as determining the structure of these clans by DNA sequence analysis. Subsequently we plan to use these clones to purify the cardiac muscle transcript homologous to them. The transcript will be used to construct a cDNA library with the purpose of determining the structure of the cardiac transcript. With regard to the anion transporter, we have observed that our cDNA probes to the erythroid anion transporter detect an mRNA of approximately the same size in cardiac muscle. Using an approach analogous to that outlined above for ankyrin, we plan to isolate the cardiac mRNA, construct a cDNA library and determine its structure with respect to that of the chicken anion transporter. Thus far we are close to completing the primary structure of the chicken molecule through DNA analysis.